FDA, NCRC Scientists Collaborate On New Standards For Salmonella-Free Tomatoes

FDA, NCRC Scientists Collaborate On New Standards For Salmonella-Free Tomatoes

March 09, 2013

Scientists with the NC State University Plants for Human Health Institute and its NC Cooperative Extension outreach component, located at the NC Research Campus in Kannapolis, are collaborating with the US Food and Drug Administration on a joint project to establish new standards to prevent Salmonella contamination of tomatoes.

From the fields and waterways of three North Carolina research farms, new guidelines for growing, harvesting, packing and shipping tomatoes free of contaminates like Salmonella are taking root.

A team of scientists from the United States Food and Drug Administration (FDA) and the NC State University (NCSU) Plants for Human Health Institute (PHHI) are working on a joint, three-year project that started in June 2012 entitled Environmental Sample Collections on Research Extension Station Tomato Farms Located in North Carolina. The goal of the project is to establish “science-based standards for growing, harvesting, packing and holding produce on domestic and foreign farms,” which is one of the main goals for all fresh produce in the 2011 Food Safety Modernization Act.

Located on the NC Research Campus in Kannapolis, PHHI is comprised of research programs and a dedicated NC Cooperative Extension group, which includes communication, farm and agribusiness management and food safety professionals.

“We are looking at some postharvest handling and postharvest water with tomatoes,” said Diane Ducharme, Good Agricultural Practices (GAPs) program coordinator and extension associate in horticulture and food safety with PHHI. “We are looking at how, within the food system, microbes might actually contact the surface of tomatoes and be incorporated into the plant, and (we are looking at) mechanisms for remediation.”

Ducharme is leading the joint project as part of her doctoral work in horticultural food science and family consumer science concentrating on fresh produce safety, which has been her area of expertise as an extension agent. She is also a co-chair of the NC Fresh Produce Safety Task Force.

Along with Penelope Perkins-Veazie, PhD, PHHI postharvest physiologist and NCSU professor in the Department of Horticultural Science, Ducharme is part of a team of scientists from PHHI and the University of Tennessee Institute of Agriculture who are working on a $2 million grant from the US Department of Agriculture’s Organic Research and Extension Initiative. The project, Alternative Post-harvest Washing Solutions to Enhance the Microbial Safety and Quality of Organic Fresh Produce, is researching “alternative organic antimicrobials” that can be used as natural substances in postharvest wash water to reduce pathogens like E. coli, Listeria and Salmonella. Read the full story about this research project.

The Danger of Salmonella

The number of incidents of Salmonella Enteritidis and Typhimurium outbreaks connected to tomatoes, Alfalfa sprouts and cantaloupes have risen over the last decade. In Florida and on the eastern shore of Virginia, scientists like Perkins-Veazie have seen the concentrations of Salmonella Newport in these areas consistently increase and are anxious to find out why it’s happening and how to prevent it.

Prevention is important since, according to the Centers for Disease Control and Prevention, Salmonella is one of the most common sources of foodborne illness causing up to 1.2 million cases every year in the United States. Salmonella lives in the intestines of humans and animals. On a farm, animal feces can easily wash into water sources or shift from pastures to neighboring fields either by feet or the air.

Infection with Salmonella, called Salmonellosis, causes diarrhea, fever and cramps within 12 to 72 hours of exposure that lasts for several days. Most people recover fully from an infection, some people require hospitalization and up to 400 people die annually in the US from Salmonellosis. Still, others develop a chronic condition called reactive arthritis from Salmonellosis.

Even though there have been very few incidents of Salmonella connected to North Carolina’s tomato industry, Salmonella is present on the state’s farms. Since North Carolina is the fifth largest tomato producer in the country and most of the tomato growers are family farms, preventing any health consequences and economic losses from an outbreak is a priority.

First and Future Findings

The first environmental samples taken from the three research stations in the study supported previous research findings that pinpoint water used for irrigation as a source of contamination. North Carolina has a network of 16 research stations operated by the NC Department of Agriculture and Consumer Services that cross the state and provide a unique setting for field studies not available elsewhere in the US. Ducharme’s analysis also found Salmonella in the sediment exposed to the water.

“In North Carolina, we do a lot of surface water irrigation,” said Ducharme. “If we are looking at surface water that could potentially be contaminated, we’re looking at mechanisms that they (the growers) have to remediate before they can ever apply water.”

This study will also look for answers to the best microbial indicator for contaminated water. The FDA proposes generic E. coli as the best pathogenic indicator. Ducharme is studying whether or not “Salmonella or a panel of pathogens could be a more effective indicator for contamination associated with tomato production.”

The study is following tomatoes from the fields to the distribution houses where they are washed and packed for shipping. “We have a chart that shows tomatoes going to three to five brokerage houses until they get to the final retailer, anywhere up and down the East Coast,” Ducharme said. “They could be in three locations overnight.”

“It’s interesting,” Perkins-Veazie added, “how much handling and temperature variation the tomatoes are exposed to and all of the things that could possibly be introduced.”

By the end of the three-year project, Ducharme and Perkins-Veazie predict that the North Carolina data coupled with similar data from Florida will be combined for an East Coast database and genome map of Salmonella.

“We’re also looking at metagenomic information,” Perkins-Veazie said. “Because we know that some species can out compete other species. We are looking at all of the populations that could be on the tomato plant, blossoms or fruit. We are finding if they are more resilient or less resilient than other species of plant pathogens or bacteria in the environment. We’ll have that data this coming year.”

As more data is collected the hope is that the guidelines and oversight that have reduced the number of Salmonella incidents in the beef, poultry, egg and dairy industries will be implemented for fresh produce. The best outcome of the joint project, Perkins-Veazie said, is that it will help tomato growers everywhere “manage contaminates inherent to growing in the environment,” ensuring that tomatoes continue to be appreciated for their health benefits and not feared for any health consequences.